rculist: Fix list_entry_rcu to read ptr with, rcu_dereference_raw
Get series with b4
b4 am [email protected]Versions newest first
- v1 Latest3 patches 8 repliesIn review
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/3 | rculist: Fix list_entry_rcu to read ptr with rcu_dereference_rawinclude/ | +0 | 6 replies | |
| 2/3 | netfilter: fix list_entry_rcu usage.net/ | +1 | 2 replies | |
| 3/3 | md/bitmap: fix list_entry_rcu usage.drivers/ | +1 | 0 replies |
Reviews trailers per patch
No Reviewed-by, Acked-by or Tested-by trailers for v1 yet.
Cover letter [PATCH 0/3] rculist: Fix list_entry_rcu to read ptr with, rcu_dereference_raw
Hi Paul and Josh,
While running some benchmarks with rcu, I noticed that rculist had a performance issue compared to the non-rcu list. Having a closer look at the rlulist, I found that there is a bad usage of rcu_dereference_raw in list_entry_rcu(). Indeed, "typeof (*ptr) *__ptr = ptr;" reads ptr and "rcu_dereference_raw(__ptr)" forces read on the stack variable __ptr. However, ptr should be read with rcu_dereference_raw not the __ptr.
This was introduced some years ago with commit 67bdbffd (2010-02-25).
I am proposing to revert this part of the patch but probably this can be fixed differently.
Fixing this showed 2 problems in the usage of list_entry_rcu.
Since it touches other parts of kernel, I guess it requires ack from other maintainers.
Thanks.
PS: I will Cc the others maintainers when somebody confirms the problem.